SIGNAL LEVEL RESPONSIVE CIRCUIT

摘要

A signal level responsive circuit including a Schmitt trigger-type circuit is provided which acts both as a signal level responsive circuit and a phase detector by energizing at least one of the current control devices of the circuit with a pulsed waveform voltage resembling a half-wave rectified AC voltage. The signal fed to the control input terminal of the Schmitt trigger circuit comprises a chopped waveform of the varying amplitude control signal involved, the chopped waveform also resembling a half-wave rectified AC waveform whose pulses vary in amplitude with the control signal and synchronized with the pulsed energizing voltage waveform. The Schmitt trigger circuit per se most advantageously has a very small hysteresis, but the signal level responsive circuit has a much greater overall hysteresis provided by a feedback circuit which increases the effective amplitude variation of the control signal after the Schmitt trigger circuit is triggered into its unstable condition.